Machine for forming spiral grooves in metal pipe inner surface

Abstract

An improved machine for forming a plurality of thin, spiral grooves in the inner surface of a metal pipe. A grooving plug is inserted and held in the metal pipe in such a manner that its axial position is constant and the metal pipe, while being moved longitudinally, is pressed by a plurality of balls which rotate planetarily around the outer surface of the metal pipe at a position corresponding to the position of the grooving plug to continuously form a plurality of spiral grooves in the inner surface of the metal pipe. Thereafter, the metal pipe is finished through a die. The machine manufactures at a high rate metal pipe which has a smooth outer surface and a grooved inner surface.

What is claimed is: 
     
       1. A machine for grooving an inner surface of a moving metal pipe comprising: a tie rod insertable into said metal pipe;   a grooving plug rotatably mounted on a front end of said tie rod;   a floating plug fixedly secured to a rear end of said tie rod;   a rotary head;   a first die proposed at a position corresponding to a position of said floating plug, said first die being adapted to hold said grooving plug at a predetermined position in said rotary head;   said rotary head being disposed downstream of said first die;   a plurality of balls planetarily rotatably arranged in said rotary head to press a wall of said metal pipe against said grooving plug in said metal pipe so as to reduce a diameter of said metal pipe; and   a second die arranged downstream of said rotary head, for finishing said metal pipe thus processed.   
     
     
       2. The machine as claimed in claim 1 further comprising means for moving said grooving plug relative to said balls in an axial direction of said metal pipe. 
     
     
       3. The machine as claimed in claim 2 further comprising means for moving said first die holding said grooving plug in an axial direction of said metal pipe. 
     
     
       4. The machine as claimed in claim 1 wherein said balls are equal in diameter and are received in a groove which is cut in said rotary head coaxially with a rotating axis of said rotary head; and further comprising means for moving said first die holding said grooving plug in an axial direction of said metal pipe.   
     
     
       5. The machine as claimed in claim 4 in which said groove receiving said balls has a depth smaller than said diameter of each of said balls and is U-shaped in section. 
     
     
       6. The machine as claimed in claim 4 in which said groove receiving said balls is V-shaped in section. 
     
     
       7. The machine as claimed in claim 1 wherein said balls are received in a recess in said rotary head, a diameter of said recess decreasing gradually in a direction of movement of said metal pipe, and further comprising a push ring, said balls being supported by being pushed by one end face of said push ring from a side of a major diameter of said recess, said one end face of said push ring being perpendicular to an axial line of said push ring; a holder; and means for moving said first die holding said grooving plug in an axial direction of said metal pipe, said first die being supported by said holder. 
     
     
       8. The machine as claimed in claim 7 further comprising a bearing and an adjusting ring for coupling said push ring to said holder. 
     
     
       9. The machine as claimed in claim 7 further comprising a bearing, an adjusting ring, a cylinder, a hollow piston, and means for moving said hollow piston, said push ring being coupled through said bearing and said adjusting ring to said hollow piston. 
     
     
       10. The machine as claimed in claim 2 or 4 wherein said means for moving said grooving plug comprises a holder for supporting said first die, and a plurality of guides for guiding movement of said holder. 
     
     
       11. The machine as claimed in claim 3 or 7 wherein said means for moving said first die comprises a holder for supporting said first die and a plurality of guides for guiding movement of said holder. 
     
     
       12. The machine as claimed in claim 1 further comprising first and second guides disposed on said front end of said tie rod and on opposite sides of said grooving plug, said first guide having an outside diameter that is smaller than an inside diameter of grooves formed in said metal pipe, and said second guide having an outside diameter substantially equal to an outside diameter of said grooving plug.